1. Field of the Invention
The present invention relates to an exhaust heat utilization method for a carbon dioxide recovery process.
2. Description of the Related Art
Conventionally, a large amount of exhaust heat generated in a process of recovering carbon dioxide from a combustion exhaust gas is cooled with cooling water. In a local area where a large amount of cooling water cannot be ensured, a large amount of exhaust heat is cooled using air cooling. Hence, a large amount of low-temperature exhaust heat is discarded without being utilized.
As a system for supplying hot water to a local, conventionally, one shown in FIG. 4 is employed in which heat generated by a power plant is utilized.
More specifically, steam of a boiler 101 is supplied to a steam turbine 102, so a generator 103 generates electricity. The steam is condensed by a condenser 104 and returned to the boiler 101 by a pump 105. The low-pressure steam is extracted from the steam turbine 102 and exchanges heat with water returned from local hot water by a heat exchanger 106. The returned local hot water is thus heated and provided as local hot water. The condensate obtained from the heat exchanged low-pressure steam is returned to the boiler 101 by a pump 107.
In the conventional local hot water system, since the low-pressure steam is extracted from the steam turbine 102, an output from the steam turbine 102 decreases. Consequently, the power generation amount decreases.
It is an object of the present invention to provide an exhaust heat utilization method for a carbon dioxide recovery process, with which returning hot water is heated by utilizing a large amount of exhaust heat generated in a process of recovering carbon dioxide from combustion exhaust gas, so a large amount of hot water to be supplied for local heating or the like can be obtained.
According to an aspect of the present invention, there is provided, an exhaust heat utilization method for a carbon dioxide recovery process, comprising:
providing a carbon dioxide recovery unit comprising a cooling tower, an absorption tower for absorbing a carbon dioxide with an absorbing liquid, and a regeneration tower for regenerating a absorbing liquid;
supplying a combustion exhaust gas to the cooling tower to cool the combustion exhaust gas;
supplying the cooled combustion exhaust gas to the absorption tower so as to come into contact with a regenerated absorbing liquid supplied from the regeneration tower to absorb carbon dioxide in the combustion exhaust gas with the regenerated absorbing liquid, thereby storing a carbon dioxide-absorbed absorbing liquid in a bottom of the absorption tower;
heating the carbon dioxide-absorbed absorbing liquid by heat exchange with the regenerated absorbing liquid supplied from the regeneration tower;
supplying the heated carbon dioxide-absorbed absorbing liquid to the regeneration tower;
heating the bottom of the regeneration tower using saturated steam to separate the carbon dioxide-absorbed absorbing liquid into carbon dioxide and a regenerated absorbing liquid; and
discharging and recovering separated carbon dioxide from the regeneration tower,
wherein returning hot water is heated by at least one heat exchange selected from heat exchange with the regenerated absorbing liquid after heat exchange, heat exchange with carbon dioxide exhausted from the regeneration tower, and heat exchange with saturated water after heating the bottom of the regeneration tower, thereby obtaining hot water.
In the exhaust heat utilization method for the carbon dioxide recovery process according to the present invention, as the combustion exhaust gas, use of one exhausted from a boiler or gas turbine of a power plant is allowed.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.